Got back to reading Woodward's book, and read the bit about the tuning fork experiment. I had a thought on a variation i wanted an opinion on.

Properly designed a length vibrating will have varying distances it moves over. Put a capacitor pack on a slide that moves up and down. A spring will pull it along the length.

The cap pack is run down the tuning fork with and without being powered. The tone will change, and where the transients match with the acoustics properly, you'll see odd signals on the runs with the power on.

I'm thinking a tuning fork would be an effective way to observe small shifts in mass. Power the "active mass" in phase lock with the tuning fork. If the Woodward effect is real there should be a shift in frequency as the "active mass" is turned on and off, or shifted in phase relative to the tuning fork oscillation. To be experimentally significant, the observed mass shift needs to be well in excess of the equivalent from the energy fed to the capacitor.

That was the thought. A tuning fork experiment was tried, but I got the impression it wasn't set up well.

Part of what makes this setup different is the fork and cap pack will find their own resonance as the pack moves.

Any change simply from charging the capacitors should be easily filterable. The important thing is to run the caps in a non- Machian regime to heat them up and characterize the thermal changes that will happen as the caps are run-- this gives you the profiles to filter.

I'm thinking it'll be much easier to adjust the electric signal to the capacitor than deal with moving the capacitor. Self resonance of the capacitor plus feed line would be a much higher frequency than the tuning fork anyway.

Running the capacitor off mechanical resonant frequency to measure any effect would be a useful control to detect some kinds of artifact. I'd also try running with a static DC charge, though I don't really expect a measurable effect with that. No charge on the capacitor is the main control reference.

So, got the book out of my work bag and looked it up, it's the "Mach guitar" design one of Cramer's students did. Apparently his setup was crap for multiple reasons, but I'm thinking it's worth exploring the setup's potential at least in theory.

The tuning fork here could be looked at as a pendulum with a very high frequency oscillation. This puts it with the other pendulum experiments done, so shares some of those issues/advantages, and I think offers some room for better signal.

The mach effect scales with frequency. The problem is, with the thermal and other issues you have, it'seems hard to get things exactly right. Your resonant frequency changes as these effect occur. The sliding capacitor deals with this-it doesn't matter where the exact resonant point is, it will pass through a point where the amplitude of the tuning fork is matching the Mach effect(the tuning fork has a longer amplidude at the end than closer to the base). You will get points where your mass fluctuations are straddling the vibration, and coming out partly on one side or another. These points should be obvious when looking at the changes in tone coming from the fork.

You still have frequency limits, and it appears there's limits to just how high you can get a tuning fork or such resonator to go, but such a "tack driver" might make sense for an ameteur experiment before building a "sledgehammer" thruster.

A tuning fork has a resonant frequency dependent on mechanical stiffness (which may be impacted measurably by temperature), and mass. In the experiment I'm thinking of that mass would include the "transient mass" device under test. The tuning fork itself would be driven by a well known tuning fork oscillator mechanism. The effect, if any, would be greatest when transient mass is greatest while the tuning fork arms are under greatest acceleration. All we'd be looking for here is a shift in resonant frequency as the test device is driven in different ways.

This test is quite different from any pendulum based test I'm familiar with for such devices, which involve pulsing the device at the resonant frequency of the pendulum, which is much slower than the operating frequency of the test device.